Effects of head-elevated position on tracheal intubation using a McGrath MAC videolaryngoscope in patients with a simulated difficult airway: a prospective randomized crossover study.

BACKGROUND: The head-elevated laryngoscopy position has been described to be optimal for intubation, particularly in obese patients and those with anticipated difficult airways. Horizontal alignment of the external auditory meatus and sternal notch (AM-S) can be used as endpoints for optimal positioning. Thus, we aligned the head-elevated position with the AM-S in the horizontal plane and evaluated its effect on laryngeal visualization and ease of intubation using a McGrath MAC videolaryngoscope in patients with a simulated difficult airway. METHODS: Sixty-four patients were included in this prospective, crossover, randomized controlled trial. A cervical collar was used to restrict neck movement and mouth opening. The head-elevated position was achieved by raising the back section of the operation room table and ensuring that the end point was horizontally aligned with the AM-S (table-ramp method). The laryngeal view was randomly assessed in both head-flat and head-elevated positions based on the percentage of glottic opening (POGO) score and modified Cormack-Lehane (MCL) grade. External laryngeal manipulation was not permitted when laryngeal visualization was scored. The trachea was intubated only once (in the second position). The ease of intubation was assessed based on the need for optimization maneuvers, intubation difficulty scale (IDS) scores and time to intubation. RESULTS: The mean table-ramp angle required to achieve the horizontal alignment of AM-S was 17.5 ± 4.1°. The mean POGO score improved significantly in the head-elevated position (59.4 ± 23.8%) when compared with the head-flat position (37.5 ± 24%) (P <  0.0001). MCL grade 1 or 2a was achieved in 56 (85.9%) and 28 (43.7%) of patients in the head-elevated and head-flat positions, respectively (P <  0.0001). Optimization maneuvers for intubation were required in 7 (21.9%) and 17 (53.1%) patients in the head-elevated and head-flat positions, respectively (P <  0.0001). The IDS scores and time to intubation did not differ significantly between the two positions. CONCLUSION: In the head-elevated position, aligning the AM-S in the horizontal plane consistently improved laryngeal visualization without worsening the view when the McGrath MAC videolaryngoscope was used in patients with simulated difficult airways. It also improved the ease of intubation, which reduced the need for optimization maneuvers. TRIAL REGISTRATION: This trial was registered with www. CLINICALTRIALS: gov , NCT04716218 , on 20/01/2021.

The influence of positive end-expiratory pressure (PEEP) in predicting fluid responsiveness in patients undergoing one-lung ventilation.

Background: Dynamic preload parameters such as pulse pressure variation (PPV) and stroke volume variation (SVV) have widely been used as accurate predictors for fluid responsiveness in patients under mechanical ventilation. To circumvent the limitation of decreased cyclic change of intrathoracic pressure, we performed an intermittent PEEP challenge test to evaluate whether PPV or SVV can predict fluid responsiveness during one-lung ventilation (OLV). Methods: Forty patients undergoing OLV were analyzed. Baseline hemodynamic variables including PPV and SVV and respiratory variables were recorded after chest opening in lateral position under OLV (T1). Five minutes after application of PEEP 10 cmH2O, the parameters were recorded (T2). Thereafter, PEEP was withdrawn to 0 cmH2O for 5 minutes (T3), and fluid loading was performed with balanced crystalloid solution 6 mL/kg of ideal body weight for 5 minutes. Five minutes after completion of fluid loading, all variables were recorded (T4). The patient was classified as fluid responder if SV increased ≥10% after fluid loading and as non-responder if SV increased <10%. Results: Prediction of fluid responsiveness was evaluated with area under the receiver operating characteristic (ROC) curve (AUC). Change in stroke volume variation (ΔSVV) showed AUC of 0.9 (P < 0.001), 95% CI = 0.82-0.99, sensitivity = 88%, specificity = 82% for discrimination of fluid responsiveness. Change in pulse pressure variation (ΔPPV) showed AUC of 0.88 (P < 0.001), 95% CI = 0.78-0.97, sensitivity = 83%, specificity = 72% in predictability of fluid responsiveness. Cardiac index and stroke volume were well maintained after PEEP challenge in non-responders while they increased in responders. Conclusions: ΔPPV and ΔSVV induced by PEEP challenge are reliable parameters to predict fluid responsiveness as well as very good predictors of fluid unresponsiveness during OLV.

Effects of silver nanoparticles on pregnant dams and embryo-fetal development in rats.

Although the potential risk of silver nanoparticles (AgNPs) to humans has recently increased due to widespread application, the potential effects of AgNPs on embryo-fetal development have not yet been determined. This study investigated the potential effects of AgNPs on pregnant dams and embryo-fetal development after maternal exposure on gestational days (GD) 6-19 in rats. AgNPs were administered to pregnant rats by gavage at concentrations of 0, 100, 300, and 1000 mg/kg/day. All dams were subjected to Cesarean section on GD 20 and the fetuses were examined for signs of embryotoxic and teratogenic effects. Examinations of hepatic oxidant/antioxidant balance and serum biochemistry were also added to the routine developmental toxicity study. Treatment with AgNPs caused a decrease in catalase and glutathione reductase activities at ≥100 mg/kg/day and a reduction in glutathione content at 1000 mg/kg/day in maternal liver tissues. However, no treatment-related deaths or clinical signs were observed in any of the animals treated with AgNPs. No treatment-related differences in maternal body weight, food consumption, gross findings, serum biochemistry, organ weight, gestation index, fetal deaths, fetal and placental weights, sex ratio, or morphological alterations were observed between the groups. The results show that repeated oral doses of AgNPs during pregnancy caused oxidative stress in hepatic tissues at ≥100 mg/kg/day, but did not cause developmental toxicity at doses of up to 1000 mg/kg/day. The no-observed-adverse-effect level of AgNPs is considered to be <100 mg/kg/day for dams and 1000 mg/kg/day for embryo-fetal development.